Halogenated Pyrazolo[1,5-A]Pyrimidines, Processes, Uses, Compositions and Intermediates

ABSTRACT

The invention provides novel halogenated pyrazolo[1,5-a]pyrimidines of formula (I) wherein R, R 1 , X and Y have different meanings, and pharmaceutically acceptable salts thereof. Compounds of formula (I) are useful for treating or preventing anxiety, epilepsy and sleep disorders including insomnia, and for inducing sedation-hypnosis, anesthesia, sleep and muscle relaxation. The invention also provides synthetic procedures for preparing said compounds and certain intermediates, as well as intermediates themselves.

TECHNICAL FIELD

This invention is directed to agents with affinity for GABA_(A) receptor, specifically to halogenated pyrazolo[1,5-a]pyrimidines, and more specifically to [7-(3-amino-4-halophenyl)-pyrazolo[1,5-a]pyrimidin-3-yl]-thiophen-2-yl-methanone acyl and sulfonyl compounds.

BACKGROUND OF THE INVENTION

GABA_(A) receptor (γ-aminobutyric acid_(A)) is a pentameric protein which forms a membrane ion channel. GABA_(A) receptor is implicated in the regulation of sedation, anxiety, muscle tone, epileptogenic activity and memory functions. These actions are due to defined subunits of GABA_(A) receptor, particularly the α₁- and α₂-subunits.

Sedation is modulated by the α₁-subunit. Zolpidem is characterized by a high affinity for the α₁-receptors and its sedative and hypnotic action is mediated by these receptors in vivo. Similarly, the hypnotic action of zaleplon is also mediated by the α₁-receptors.

The anxiolytic action of diazepam is mediated by the enhancement of GABAergic transmission in a population of neurons expressing the α₂-receptors. This indicates that the α₂-receptors are highly specific targets for the treatment of anxiety.

Muscle relaxation in diazepam is mainly mediated by α₂-receptors, since these receptors exhibit a highly specific expression in spinal cord. The anticonvulsant effect of diazepam is partly due to α₁-receptors. In diazepam, a memory-impairing compound, anterograde amnesia is mediated by α₁-receptors.

GABA_(A) receptor and its α₁- and α₂-subunits have been widely reviewed by H. Möhler et at. (J. Pharmacol. Exp. Ther., 300, 2-8, 2002); H. Möhler et at. (Curr. Opin. Pharmacol., 1, 22-25, 2001); U. Rudolph et al. (Nature, 401, 796-800, 1999); and D. J. Nutt et at. (Br. J. Psychiatry, 179, 390-396, 2001).

Diazepam and other classical benzodiazepines are extensively used as anxiolytic agents, hypnotic agents, anticonvulsants and muscle relaxants. Their side effects include anterograde amnesia, decrease in motor activity and potentiation of ethanol effects.

In this context, the compounds of this invention are ligands of α₁- and α₂-GABA_(A) receptor for their clinical application in sleep disorders, preferably insomnia, anxiety and epilepsy.

Insomnia is a highly prevalent disease. Its chronically affects 10% of the population and 30% when transitory insomnia is computed as well. Insomnia describes the trouble in getting to sleep or staying asleep and is associated with next-day hangover effects such as weariness, lack of energy, low concentration and irritability. The social and health impact of this complaint is important and results in evident socioeconomic repercussions.

Pharmacological therapy in the management of insomnia firstly included barbiturates and chloral hydrate, but these drugs elicit numerous known adverse effects, for example, overdose toxicity, metabolic induction, and enhanced dependence and tolerance. In addition, they affect the architecture of steep by decreasing above all the duration and the number of REM sleep stages. Later, benzodiazepines meant an important therapeutic advance because of their lower toxicity, but they still showed serious problems of dependence, muscle relaxation, amnesia and rebound insomnia following discontinuation of medication.

The latest known therapeutic approach has been the introduction of non-benzodiazepine hypnotics, such as pyrrolo[3,4-b]pyrazines (zopiclone), imidazo[1,2-a]pyridines (zolpidem) and, finally, pyrazolo[1,5-a]pyrimidines (zaleplon). Later, two new pyrazolo[1,5-a]pyrimidines, indiplon and ocinaplon, have entered into development, the latter with rather anxiolytic action. All these compounds show a rapid steep induction and have less next-day hangover effects, lower potential for abuse and tower risk of rebound insomnia than benzodiazepines. The mechanism of action of these compounds is the alosteric activation of GABA_(A) receptor through its binding to benzodiazepine binding site (C. F. P. George, The Lancet, 358, 1623-1626, 2001). While benzodiazepines are unspecific ligands at GABA_(A) receptor binding site, zolpidem and zaleplon show a greater selectivity for α₁-subunit. Notwithstanding that, these drugs still affect the architecture of steep and may induce dependence in long-term treatments.

The present invention is structurally related to, but patentably distinct from the compound N-{3-[3-(thiophene-2-carbonyl)-pyrazolo[1,5-a]pyrimidin-7-yl]-phenyl}-N-methyl-acetamide, indiplon, which is described in U.S. Pat. No. 6,399,621, and the compounds N-{3-[3-(thiophene-2-carbonyl)-pyrazolo[1,5-a]pyrimidin-7-yl]-phenyl}-N-methyl-methanesulfonamide and N-{3-[3-(thiophene-2-carbonyl)-pyrazolo[1,5-a]pyrimidin-7-yl]-phenyl}-N-prop-2-ynyl-methanesulfonamide, which are described in WO 2005014597, examples 3 and 16 respectively, because of their improved properties as shown in the Detailed Description of the Invention. Similar compounds to indiplon had been disclosed previously in U.S. Pat. No. 4,521,422.

Research for new active compounds in the management of insomnia answers an underlying health need, because even recently introduced hypnotics still affect the architecture of sleep and may induce dependence in long-term treatments.

It is therefore desirable to focus on the development of new hypnotic agents with a lower risk of side effects.

Thus, the present invention is directed to new halogenated pyrazolo[1,5-a]pyrimidines which are active versus GABA_(A) and, particularly, versus its α₁- and α₂-subunits. Consequently, the compounds of this invention are useful in the treatment and prevention of all those diseases mediated by GABA_(A) receptor α₁- and α₂-subunits. Non-limitative examples of such diseases are sleep disorders, preferably insomnia, anxiety and epilepsy. Non-limitative examples of the relevant indications of the compounds of this invention are all those diseases or conditions, such as insomnia or anesthesia, in which an induction of sleep, an induction of sedation or an induction of muscle relaxation are needed.

SUMMARY OF THE INVENTION

The present invention describes a novel class of compounds represented by formula (I):

and pharmaceutically acceptable salts thereof, wherein R, R₁, X and Y are defined below, which are ligands of GABA_(A) receptor.

It is another object of this invention to provide novel methods of treating or preventing anxiety, epilepsy and sleep disorders including insomnia, and for inducing sedation-hypnosis, anesthesia, sleep and muscle relaxation by administering a therapeutically effective amount of a compound of formula (I) or a pharmaceutically acceptable salt thereof. Synthetic procedures for preparing said compounds and certain intermediates are also within the scope of the invention. Relevant intermediates themselves also constitute another object of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to novel [7-(3-amino-4-halophenyl)-pyrazolo[1,5-a]pyrimidin-3-yl]-thiophen-2-yl-methanone acyl and sulfonyl compounds of formula (I):

wherein R represents an alkyl(C₁-C₆); R₁ is selected from the group consisting of alkyl(C₁-C₆) and alkynyl(C₁-C₆); X represents a halogen atom; and Y is selected from the group consisting of —CO— and —SO₂—; and a pharmaceutically acceptable salt thereof.

Preferably R is methyl; R₁ is selected from methyl and prop-2-ynyl; and X is selected from fluorine and chlorine.

The term “pharmaceutically acceptable salt” used herein encompasses any salt formed from organic and inorganic acids, such as hydrobromic, hydrochloric, phosphoric, nitric, sulfuric, acetic, adipic, aspartic, benzenesulfonic, benzoic, citric, ethanesulfonic, formic, fumaric, glutamic, lactic, maleic, malic, malonic, mandelic, methanesulfonic, 1,5-naphthalendisulfonic, oxalic, pivalic, propionic, p-toluenesulfonic, succinic, tartaric acids and the like.

The present invention comprises the compounds:

-   N-{2-fluoro-5-[3-(thiophene-2-carbonyl)-pyrazolo[1,5-a]pyrimidin-7-yl]-phenyl}-N-methyl-acetamide; -   N-{2-chloro-5-[3-(thiophene-2-carbonyl)-pyrazolo[1,5-a]pyrimidin-7-yl]-phenyl}-N-methyl-acetamide; -   N-{2-fluoro-5-[3-(thiophene-2-carbonyl)-pyrazolo[1,5-a]pyrimidin-7-yl]-phenyl}-N-methyl-methanesulfonamide; -   N-{2-chloro-5-[3-(thiophene-2-carbonyl)-pyrazolo[1,5-a]pyrimidin-7-yl]-phenyl}-N-methyl-methanesulfonamide;     and -   N-{2-fluoro-5-[3-(thiophene-2-carbonyl)-pyrazolo[1,5-a]pyrimidin-7-yl]-phenyl}-N-prop-2-ynyl-methanesulfonamide.

Another embodiment of the present invention is to provide a process for preparing the compounds of formula (I) and their pharmaceutically acceptable salts.

The compounds of the present invention can be used for treating or preventing diseases associated with GABA_(A) receptor modulation in a mammal which comprises administering to said mammal in need thereof an effective amount of a compound of formula (I) or a pharmaceutically acceptable salt thereof. More specifically, diseases associated with GABA_(A) receptor modulation comprise diseases associated with α₁-GABA_(A) receptor modulation and/or α₂-GABA_(A) receptor modulation. A non-limitative list of such diseases comprises anxiety, epilepsy, steep disorders, including insomnia, and the like.

Another embodiment of the present invention is to provide the use of a compound of formula (I) for treating or preventing anxiety in a mammal in need thereof which comprises administering to said mammal an effective amount of said compound or a pharmaceutically acceptable salt thereof.

Another embodiment of the present invention is to provide the use of a compound of formula (I) for treating or preventing epilepsy in a mammal in need thereof which comprises administering to said mammal an effective amount of said compound or a pharmaceutically acceptable salt thereof.

Another embodiment of the present invention is to provide the use of a compound of formula (I) for treating or preventing sleep disorders in a mammal in need thereof which comprises administering to said mammal an effective amount of said compound or a pharmaceutically acceptable salt thereof.

Another embodiment of the present invention is to provide the use of a compound of formula (I) for treating or preventing insomnia in a mammal in need thereof which comprises administering to said mammal an effective amount of said compound or a pharmaceutically acceptable salt thereof.

Another embodiment of the present invention is to provide the use of a compound of formula (I) for inducing sedation-hypnosis in a mammal in need thereof which comprises administering to said mammal an effective amount of said compound or a pharmaceutically acceptable salt thereof.

Another embodiment of the present invention is to provide the use of a compound of formula (I) for inducing anesthesia in a mammal in need thereof which comprises administering to said mammal an effective amount of said compound or a pharmaceutically acceptable salt thereof.

Another embodiment of the present invention is to provide the use of a compound of formula (I) for modulating the necessary time to induce sleep and its duration in a mammal in need thereof which comprises administering to said mammal an effective amount of said compound or a pharmaceutically acceptable salt thereof.

Another embodiment of the present invention is to provide the use of a compound of formula (I) for inducing muscle relaxation in a mammal in need thereof which comprises administering to said mammal an effective amount of said compound or a pharmaceutically acceptable salt thereof.

The present invention also relates to a method of treatment or prevention of a mammal suffering from diseases associated with GABA_(A) receptor modulation in a mammal, which comprises administering to said mammal in need thereof a therapeutically effective amount of a compound of formula (I) or a pharmaceutically acceptable salt thereof, together with pharmaceutically acceptable diluents or carriers. More specifically, diseases associated with GABA_(A) receptor modulation comprise diseases associated with α₁-GABA_(A) receptor modulation and/or α₂-GABA_(A) receptor modulation. A non-limitative list of such diseases comprises anxiety, epilepsy, sleep disorders, including insomnia, and the like.

As used herein, the term “mammal” shall refer to the Mammalia class of higher vertebrates. The term “mammal” includes, but is not limited to, a human.

Another embodiment of the present invention is to provide a pharmaceutical composition containing a compound of formula (I) or a pharmaceutically acceptable salt thereof in association with therapeutically inert carriers.

Another embodiment of the present invention is to provide a process for preparing intermediate compounds of formula (VI):

wherein R, R₁, X and Y are as defined above.

The specific intermediate compounds (VI), namely:

-   N-[5-(3-dimethylamino-acryloyl)-2-fluoro-phenyl]-N-methyl-acetamide; -   N-[2-chloro-5-(3-dimethylamino-acryloyl)-phenyl]-N-methyl-acetamide; -   N-[5-(3-dimethylamino-acryloyl)-2-fluoro-phenyl]-N-methyl-methanesulfonamide; -   N-[2-chloro-5-(3-dimethylamino-acryloyl)-phenyl]-N-methyl-methanesulfonamide;     and -   N-[5-(3-dimethylamino-acryloyl)-2-fluoro-phenyl]-N-prop-2-ynyl-methanesulfonamide     constitute another embodiment of the invention.

The compositions include those suitable for oral, rectal and parenteral (including subcutaneous, intramuscular, and intravenous) administration, although the most suitable route will depend on the nature and severity of the condition being treated. The most preferred route of the present invention is the oral route. The compositions may be conveniently presented in unit dosage form, and prepared by any of the methods well known in the art of pharmacy.

The active compound can be combined with a pharmaceutical carrier according to conventional pharmaceutical compounding techniques. The carrier may take a wide variety of forms depending on the form of the preparation desired for administration, e.g. oral or parenteral (including intravenous injections or infusions). In preparing the compositions for oral dosage form any of the usual pharmaceutical media may be employed. Usual pharmaceutical media include, for example, water, glycols, oils, alcohols, flavoring agents, preservatives, coloring agents, and the like in the case of oral liquid preparations (such as for example, suspensions, solutions, emulsions and elixirs); aerosols; or carriers such as starches, sugars, microcrystalline cellulose, diluents, granulating agents, lubricants, binders, disintegrating agents and the like, in the case of oral solid preparations (such as for example, powders, capsules, and tablets) with the oral solid preparations being preferred over the oral liquid preparations.

Because of their ease of administration, tablets and capsules represent the most advantageous oral dosage unit form, in which case solid pharmaceutical carriers are employed. If desired, tablets may be coated by standard aqueous or nonaqueous techniques.

A suitable dosage range for use is from about 0.01 mg to about 100.00 mg total daily dose, given as a once daily administration or in divided doses if required.

The compounds of general formula (I) may be prepared according to the reaction shown in Scheme 1.

In the intermediates of formula (II), R, R₁, X and Y are as defined in (I) and Q is an appropriate leaving group selected from the group consisting of N(dialkyl(C₁-C₆)), alkylthio(C₁-C₆) and alkoxy(C₁-C₆). Preferably Q is selected from the group consisting of dimethylamino, methylthio and methoxy. The treatment of the resulting compounds in the form of free base with an acid affords the corresponding salt thereof.

The reaction of aminopyrazole (III) with appropriately substituted 1-aryl-2-propen-1-one (II) is carried out in an inert polar protic or aprotic solvent such as glacial acetic acid, ethanol, methanol, dimethylformamide or dimethylsulfoxide at a temperature ranging from 50° to 130° C. After elapsing several hours (reaction time), the solvent is removed and the residue obtained is partitioned between an aqueous solution of sodium bicarbonate and dichloromethane. The crude resulting from evaporating the organic layer to dryness may be purified by one of the following methods: (a) silica get chromatography using ethyl acetate or dichloromethane/methanol as eluent; or (b) crystallization in a suitable solvent (ethyl acetate, ethanol, methanol, etc.).

The intermediate of formula (II) when Q is dimethylamino [intermediate (VI)] can be obtained following the reaction sequence shown in Scheme 2.

wherein R, R₁, X and Y are as described above.

The intermediates of formula (IV) when Y is a sulfonyl group [intermediates (IV′)] are prepared according to the method described by R. H. Uloth et at (J. Med. Chem. 9, 88-96, 1966).

The alkylation of the intermediates (IV) leading to the intermediates of formula (V) is performed via formation of an anion and subsequent reaction with an alkyl halide.

The enaminones of formula (V′) and (VI) are prepared by reacting the corresponding acetophenones (IV) and (V) respectively with N,N-dimethylformamide dimethylacetal (DMFDMA) or Bredereck's reagent (tert-butoxybis(dimethylamino)methane).

The intermediates of formula (II), when Q is dimethylamino, Y is sulfonyl and R₁ is methyl[intermediates (VII)], can alternatively be prepared according to Scheme 3.

The conversion of (IV′) into (VII) leads to the formation of the enaminone and, simultaneously, the formation of the N-methyl-sulfonamide as a result of the use of the properties of the N,N-dimethylformamide dimethyl acetal as a methylating agent.

The intermediates of formula (II), when Q is dimethylamino and R₁ is methyl (X), can also be prepared according to Scheme 4.

The advantage of this process is based on the fact that the formation of the sulfonamide or carboxamide takes place in the last step of the process. As a result, the total number of reaction steps is reduced in the preparation of large series of products. Moreover, as shown in the scheme, the conversion of (VIII) into (IX) leads to three following reactions in a one-pot process: (a) formation of the enaminone; (b) methylation of the trifluoroacetamide; and (c) deacylation yielding the N-methylated amine. The subsequent reaction of (IX) with the corresponding sulfonic acid or carboxylic acid chloride leads to obtaining intermediates (X).

The compounds of the present invention have a high affinity for α₁- and α₂-GABA_(A) receptors. These in vitro results are consistent with those in vivo results obtained in sedation-hypnosis tests.

In accordance with the results obtained, the compounds of the present invention have evidenced pharmacological activity both in vitro and in vivo, which has been similar to or higher than that of prior-art compounds. All these results support!their use in diseases or conditions modulated by α₁- and α₂-GABA_(A) receptors, such as insomnia or anesthesia, in which an induction of sleep, an induction of sedation or an induction of muscle relaxation are needed. Furthermore, it has been found that administering the compounds of the present invention at low doses a surprising increase in the sedative-hypnotic activity is achieved over the one achieved using the compounds of the prior art (i.e. Indiplon, Zaleplon and Examples 3 and 16 from WO200501497), as it is illustrated below.

Pharmacological and cytotoxic activities, metabolic stability and pharmacokinetic profile of the compounds of the present invention have been determined as shown below.

a) Pharmacological activities

1-Ligand-binding assays. Determination of the affinity of test compounds for α₁- and α₂-GABA_(A) receptor

Male Sprague-Dawley rats weighing 200-250 g at the time of experiment were used. After decapitation, the cerebellum (tissue that mostly contains α₁-GABA_(A) receptor) and spinal cord (tissue that mostly contains α₂-GABA_(A) receptor) were removed. The membranes were prepared according to the method by J. Lameh et at. (Prog. Neuro-Psychopharmacol. Biol. Psychiatry, 24, 979-991, 2000) and H. Noguchi et al. (Eur J Pharm, 434, 21-28, 2002) with slight modifications. Once the tissues weighed, they were suspended in 50 mM Tris-HCl (pH 7.4), 1:40 (v/v), or sucrose 0.32 M in the case of spinal cord, homogenized and then centrifuged at 20000 g for 10 min at 7° C.

The resulting pellet was resuspended under the same conditions and centrifuged again. The pellet was finally resuspended on a minimum volume and kept at −80° C. overnight. On the next day, the process was repeated until the final pellet was resuspended at a ratio of 1:10 (v/v) in the case of cerebellum and at a ratio of 1:5 (v/v) in the case of spinal cord.

Affinity was determined by competitive tests using radiolabeled flumazenil as ligand. The tests were performed according to the methods described by S. Arbilla et at. (Eur. J. Pharmacol., 130, 257-263, 1986); and Y. Wu et al. (Eur. J. Pharmacol., 278, 125-132, 1995) using 96-well microtiter plates. The membranes containing the study receptors, flumazenil (radiolabeling at a final concentration of 1 nM) and ascending concentrations of test compounds (in a total volume of 230 μl in 50 mM [ph 7.4] Tris.HCl buffer) were incubated. Simultaneously, the membranes were only incubated with the radiolabeled flumazenil (total binding, 100%) and in the presence of an elevated concentration of unradiolabeled flumazenil (non-specific binding, % estimation of radiolabeled ligand). The reactions started on adding the radiolabeled ligand followed by incubation for 60 minutes at 4° C. At the end of the incubation period, 200 μl of reaction were transferred to a multiscreen plate (Millipore) and filtered using a vacuum manifold and then washed three times with cold test buffer. The multiscreen plates were equipped with a GF/B filter that retained the membranes containing the receptors and the radiolabeled ligand which had been bound to the receptors. After washing, the plates were left till dry. Once dried, scintillation liquid was added and left under stirring overnight. The next day the plates were counted using a Perkin-Elmer Microbeta scintillation counter.

For analysis of the results the percentage of specific binding for every concentration of test compound was calculated as follows:

% specific binding ═(X−N/T−N)×100

where, X: amount of bound ligand for every concentration of compound. T: total binding, maximum amount bound to the radiolabeled ligand. N: non-specific binding, amount of radiolabeled ligand bound in a non-specific way irrespective of the receptor used.

Every concentrations of each compound were tested in triplicate and their mean values were used to determine the experimental values of % specific binding versus the concentration of compound. Affinity data are expressed as % inhibition at 10⁻⁵M and 10⁻⁷M concentrations and Ki were obtained in some compounds, in which the ratios between α₁ and α₁ affinities were calculated. The results of these tests are given in Tables 1 and 2. Advantageously, certain compounds of the present invention show a higher selectivity as sedative-hypnotic agents towards the muscle relaxing activity as evidenced by an enhanced α₂/α₁ ratio as compared to the prior art compounds.

TABLE 1 Affinity for the α₁ subunit of GABA_(A) receptor Compound % Inhib 10⁻⁵M % Inhib 10⁻⁷M Ki (nM) Preparative example 2 100.4 95.3 2.1 Preparative example 4 99.8 60.0 57.6 Preparative example 6 99.7 88.8 1.7 Preparative example 8 93.8 40.9 — Preparative example 10 100.0 99.7 0.98 Indiplon 3.1 Zaleplon 97.2 26.1 151.4 Example 3 WO2005014597 100.4 90.6 7.4 Example 16 WO2005014597 100.0 99.9 1.3

TABLE 2 Affinity for the α₂ subunit of GABA_(A) receptor Compound % Inhib 10⁻⁵M % Inhib 10⁻⁷M Ki (nM) Preparative example 2 99.3 67.3 20.0 Preparative example 4 95.7 8.4 197.8 Preparative example 6 97.9 55.9 11.2 Preparative example 8 68.9 0.0 — Preparative example 10 100.2 97.5 1.6 Indiplon 99.2 65.7 23.8 Zaleplon 78.7 — 1528.1 Example 3 WO2005014597 99.8 58.5 36.7 Example 16 WO2005014597 100.2 87.2 22.0

In this context, the selectivity α₂/α₁ ratio for the compound from preparative example 2 is 9.6 in contrast to 7.7 for indiplon and 5.0 for the compound from example 3 in WO2005014597, thus resulting in 25% and 92% increased selectivity respectively. Consequently less side effects are expected for the present compounds.

2-In Vivo Determination of Predictive Sedative-Hypnotic Action

The in vivo effects of these compounds were assessed by a predictive sedation-hypnosis test in mice (D. J. Sanger et at., Eur. J. Pharmacol., 313, 35-42, 1996; and G. Griebet et at., Psychopharmacology, 146, 205-213, 1999).

Groups of 5-8 male CD1 mice, weighing 22-26 g at the time of testing, were used. The test compounds were administered in single equimolecular intraperitoneal doses, suspended in 0.25% agar with one drop of Tween 80 in a volume of 10 ml/kg. Two doses were tested in each route. Control animals received the vehicle alone. Using a Smart System (Panlab, S.L., Spain) the traveled distance in cm was recorded for each mouse at 5-min intervals during a period of 30 minutes after intraperitoneal (ip) dosing and 60 minutes after oral (po) dosing. The inhibition percentage of traveled distance of treated animals versus control animals (the first 5 min were discarded) was calculated. The results of this test are given in Table 3.

TABLE 3 Determination of in vivo sedative-hypnotic activity in mice. % Inhib motor activity Ip po 98 0.98 98 3 Compound μmol/kg μmol/kg μmol/kg μmol/kg Preparative example 2 94.97 81.21 92.29 84.01 Preparative example 4 90.26 — 88.71 — Preparative example 6 91.5 69.42 82.00 46.23 Preparative example 8 78.26 — — — Preparative example 10 91.6 91.94 90.22 47.89 Indiplon 88.04 70.45 82.40 73.67 Zaleplon 84.98 32.67 64.11 25.39 Example 3 WO2005014597 89.76 64.56 — — Example 16 WO2005014597 95.36 71.43 84.33 38.78

Surprisingly, relevant compounds in the present invention show an increased sedative-hypnotic activity comparatively to prior art compounds.

Particularly, the compounds of the present invention at low doses give rise to a higher increase in the sedative-hypnotic activity over the one achieved using the compounds of the prior art (i.e. Indiplon, Zaleplon and Examples 3 and 16 from WO2005014597). This is of great importance since it is possible to get the desired therapeutic effect (i.e. sedative-hypnotic) using a lower dose with the subsequent advantage that the related side-effects can be minimized.

The comparison between the compounds of the present invention and the corresponding compounds of the prior art, shows that the presence of a halogen atom in the structure represented by the formula (I) gives rise to an increase in the sedative-hypnotic activity, especially at low doses. Thus, for instance, comparing the activity of compound of Example 10 of the present invention with that obtained with the compound of Example 16 of WO2005014597, an increase higher than 20% is achieved when a low dose is used, independently of the administration route.

b) Cytotoxic Activity

In Vitro Determination of Cell Toxicity in HepG2 at 24 h

HepG2 cells (human hepatocellular carcinoma) were obtained from the American Type Culture Collection (ATCC) and cultured in Eagle's Minimum Essential Medium (Eagle) with Earle's balanced salt solution adjusted to contain 1.87 mM Glutamax™ I, 0.1 mM non-essential amino acids, 1.0 mM sodium pyruvate, 100000 U/L penicillin, 10000 μg/L streptomycin 90%; fetal bovine serum, 10%. Promega CellTiter 96® Aqueous Non-Radioactive Cell Viability Assay contains the tetrazolium compound [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt (MTS). The conversion of MTS into the aqueous soluble formazan product is accomplished by dehydrogenase enzymes found in metabolically active cells. The quantity of formazan product is directly proportional to the number of living cells in culture.

Compounds were dissolved in DMSO to achieve an initial concentration of 100 mM. Serial dilutions were made from this stock solution into DMSO to achieve concentrations of 10, 1, 0.1 and 0.01 mM. The stock solution and serial dilutions were then diluted 1:100 with cell culture medium to obtain six final assay concentrations of 1000, 100, 10, 1, 0.1 and 0.01 μM. The final DMSO concentration in all wells was 1% v/v. HepG2 cells were incubated with test compounds for 24 hours. Relative cell viability was determined spectro-photometrically at 490 nm following the addition of the MTS dye and further one-hour incubation. Tamoxifen was used as the positive control.

The percent absorbance of the samples treated with the test article was compared to the untreated sample to calculate the percentage of control. The results of this test are given in Table 4.

TABLE 4 Determination of cell toxicity in HepG2 Compound 100 μM Preparative example 2 107.19 Preparative example 4 92.86 Preparative example 6 84.31 Preparative example 8 75.39 Preparative example 10 — Indiplon 69.8 Zaleplon 97.5 Example 16 WO2005014597 53.2

Accordingly, the compounds from preparative examples 2, 4, 6 and 8 surprisingly show less cytotoxicity than prior art compounds, thus conferring a better safety profile to compounds of the present invention.

c) Metabolic Stability

In Vitro Determination Of Metabolic Stability in Human Hepatocytes Cytosolic Fraction

Compounds were dissolved in DMSO to achieve an initial concentration of 10 mM. This stock solution was then diluted with solvent and buffer to obtain final assay concentration of 5 μM. Compounds were tested at a single concentration of 5 μM in duplicate incubating with 1.0 mg/ml of pooled human cytosol (obtained from Xenotech plc) at 37° C. Metabolism was assessed in the presence or absence of cofactors and measured as loss of parent compound by LC/MS analysis at 0, 60 and 120-minutes time points. Percent parent remaining was then calculated. A generic LC method was used:

Mobile phase: A = 0.1% Formic acid in water B = 0.1% Formic acid in acetonitrile HPLC Column: Higgins Clipius C18 5 μm, 50 × 3 mm Flow rate: 2 ml · min⁻¹ Gradient: Time % A % B 0.00 95 5 2.00 5 95 2.50 5 95 2.60 95 5 3.00 95 5

The results of this test are given in Table 5.

TABLE 5 Metabolic stability in human hepatocyte cytosolic fraction Compound 60 min 120 min Preparative example 2 104 110 Preparative example 4 105 103 Preparative example 6 103 106 Indiplon 100 98 Zaleplon 79 68

Surprisingly some compounds of the present invention show an increased metabolic stability comparatively to prior art compounds, thus predicting an improved pharmacokinetic profile for the instant compounds.

d) Pharmacokinetic Profile

In Vivo Determination of Pharmacokinetic Profile After Single Dose

The compound from preparative example 2 was tested for pharmacokinetic profile following intravenous administration. Indiplon was used as reference compound. Three male Sprague-Dawley rats, weighing 250-300 g were used for each compound. The sampling was performed by retroorbital sinus puncture at the following time points 2.5, 5, 30, 60, 120, 180, 300 and 420 min post-administration. The samples were kept in an ice-bath until plasma separation. The animals were anaesthetized by isoflurane inhaled at each extraction. Plasma was separated by centrifugation (10 min, 4° C., 4500 rpm) and stored at temperature below −70° C. until analysis.

An analytical method based on an extraction of each compound by liquid-solid extraction and subsequent determination by LC/MS or LC/MS/MS using an internal standard (IS) was used.

Calculation of pharmacokinetic parameters (AUC_(0-t)=area under the curve from zero to last extraction time-point, Cl=clearance, t_(1/2)=half-life and Vd=volume of distribution) according to non-compartmental analysis was performed. The results are shown in Table 6.

TABLE 6 Pharmacokinetic parameters Parameter Compound Mean AUC_(0-t) (g*hr/L) Indiplon 0.0007 Preparative example 2 0.0011 Cl (L/hr/kg) Indiplon 3.4500 Preparative example 2 2.7442 t_(1/2) (hr) Indiplon 0.9837 Preparative example 2 1.7315 Vd (L/kg) Indiplon 2.3206 Preparative example 2 7.2442

Experimental results exhibit a quite different pharmacokinetic profile for the compound of example 2 as compared to the prior art compound Indiplon. Indeed, the area under the curve is 57% higher for the compound of the preparative example 2, thus indicating an increased exposure to the product; clearance is 20% tower meanwhile its half-life is 76% higher, thus revealing a slower elimination rate; and finally volume of distribution is 212% higher, suggesting extensive distribution to deep non-aqueous compartments (ie brain) compared to indiplon. Pharmacokinetic parameters correlate with some animal pharmacology findings. For instance, in the in vivo sedative-hypnotic activity test in mice (3 μmol/kg po) the inhibition percentage decreases from 74% (5 minutes) to 67% (60 minutes) for indiplon, in contrast said parameter remains constant at 84% for the compound from preparative example 2. Said surprising pharmacokinetic properties show that the compound of the present invention affords a better steep quality thus avoiding nocturnal awakenings and conferring a sounder and continued steep.

The following non-limiting examples illustrate the scope of the present invention.

PREPARATIVE EXAMPLE 1 N-[5-(3-Dimethylamino-acryloyl)-2-fluoro-phenyl]-N-methyl-acetamide

3.3 g (16.9 mmol) of N-(5-acetyl-2-fluoro-phenyl)-acetamide were dissolved in 8.36 ml (7.49 g) (62.89 mmol) of N,N-dimethylformamide dimethylacetal and the resultant solution was refluxed for 6.5 hours. The excess of volatile reagent was removed by reduced pressure distillation to yield a crude which was crystallized from ethyl acetate. 3.32 g of N-[5-(3-dimethylamino-acryloyl)-2-fluoro-phenyl]-acetamide as a yellowish-white solid were obtained (yield 78.6%).

¹H NMR (400 MHz, CDCl3): δ 2.21 (3H, s), 2.89 (3H, s), 3.11 (3H, s), 5.65 (1H, d, J=12.8 Hz), 7.05-7.1 (1H, m), 7.62-7.68 (2H, m), 7.77 (1H, d, J=12.4 Hz), 8.71-8.73 (1H, m).

MS (ES) m/z=251 (MH+)

HPLC=99.8%

1.5 g (5.99 mmol) of N-[5-(3-dimethylamino-acryloyl)-2-fluoro-phenyl]-acetamide were dissolved in 15 ml of dry N,N-dimethylformamide. To the solution formed at 0° C. and under inert atmosphere, 0.29 g (7.31 mmol) of sodium hydride were added. After stirring for 30 minutes, a solution of 0.94 g (6.59 mmol) of methyl iodide in 5 ml of dry N,N-dimethylformamide was added and stirring was maintained at room temperature for 5 h. The solvent was removed by reduced pressure distillation. To the resulting residue were added 30 ml of dichloromethane and 10 ml of water. The two layers were separated, and the aqueous layer was washed with 30 ml of dichloromethane. The organic layers were washed with 40 ml of water and dried over magnesium sulfate. The dichloromethane layer was evaporated to dryness to yield an oil which, crystallizing from ethyl acetate, gave 804 mg of N-[5-(3-dimethylamino-acryloyl)-2-fluoro-phenyl]-N-methyl-acetamide as a yellowish-white solid were obtained (yield 50.8%).

¹H NMR (400 MHz, CDCl3): δ 1.85 (3H, s), 2.94 (3H, s), 3.17 (3H, s), 3.22 (3H, s), 5.62 (1H, d, J=12.4 Hz), 7.16-7.25 (1H, m), 7.78-7.89 (3H, m).

MS (ES) m/z=265 (MH+)

HPLC=94.9%

PREPARATIVE EXAMPLE 2 N-{2-Fluoro-5-[3-(thiophene-2-carbonyl)-pyrazolo[1,5-a]pyrimidin-7-yl]-phenyl}-N-methyl-acetamide

A mixture of 0.073 g (0.38 mmol) of (5-amino-1H-pyrazol-4-yl)-thiophene-2-yl-methanone and 0.1 g (0.38 mmol) of N-[5-(3-dimethylamino-acryloyl)-2-fluoro-phenyl]-N-methyl-acetamide in 10 ml of glacial acetic acid was refluxed for 2.5 hours and then the solvent was removed by reduced pressure distillation. To the resulting residue were added 15 ml of dichloromethane and 10 ml of saturated sodium bicarbonate solution. The two layers were separated, and the aqueous layer was washed with 10 ml of dichloromethane. The organic layers were washed with 10 ml of water and dried over magnesium sulfate. The dichloromethane layer was evaporated to dryness to yield an oil which, in the presence of ethyl acetate, gave 112 mg of N-{2-fluoro-5-[3-(thiophene-2-carbonyl)-pyrazolo[1,5-a]pyrimidin-7-yl]-phenyl}-N-methyl-acetamide as a solid (yield 75%).

¹H NMR (400 MHz, CDCl3): δ 1.98 (3H, s,), 3.3 (3H, s), 7.13 (1H, d, J=4 Hz), 7.18-7.20 (1H, m), 7.42 (1H, t, J=8.8 Hz), 7.71 (1H, d, J=5.2 Hz), 8.02-8.08 (2H, m), 8.12 (1H, dd, J=2.4 and 7.6 Hz), 8.71 (1H, s), 8.82 (1H, d, J=4 Hz).

MS (ES) m/z=395 (MH+)

HPLC=99.2%

m.p.=165-167° C.

PREPARATIVE EXAMPLE 3 N-[2-Chloro-5-(3-dimethylamino-acryloyl)-phenyl]-N-methyl-acetamide

4.46 g (21.1 mmol) of N-(5-acetyl-2-chloro-phenyl)-acetamide were dissolved in 10.4 ml (9.34 g) (78.39 mmol) of N,N-dimethylformamide dimethylacetal and the resultant solution was refluxed for 6.5 hours. The excess of volatile reagent was removed by reduced pressure distillation to yield a crude which was crystallized from ethyl acetate. 4.53 g of N-[2-chloro-5-(3-dimethylamino-acryloyl)-phenyl]-acetamide as a yellowish-white solid were obtained (yield 80.5%).

¹H NMR (400 MHz, CDCl3): δ 2.24 (3H, s), 2.90 (3H, s), 3.12 (3H, s), 5.66 (1H, d, J=12.4 Hz), 7.38 (1H, d, J=8.8 Hz), 7.62 (1H, d, J=8.8 Hz), 7.69 (1H, s), 7.77 (1H, d, J=12.4 Hz), 8.7 (1H, s).

MS (ES) m/z=267 (MH+)

HPLC=98.3%

1.0 g (3.75 mmol) of N-[2-chloro-5-(3-dimethylamino-acryloyl)-phenyl]-acetamide were dissolved in 10 ml of dry N,N-dimethylformamide. To the solution formed at 0° C. and under inert atmosphere, 0.18 g (4.57 mmol) of sodium hydride were added. After stirring for 30 minutes, a solution of 0.59 g (4.12 mmol) of methyl iodide in 3 ml of dry N,N-dimethylformamide was added and stirring was maintained at room temperature for 5 h. The solvent was removed by reduced pressure distillation. To the resulting residue were added 30 ml of dichloromethane and 10 ml of water. The two layers were separated, and the aqueous layer was washed with 30 ml of dichloromethane. The organic layers were washed with 40 ml of water and dried over magnesium sulfate. The dichloromethane layer was evaporated to dryness to yield an oil which, crystallizing from ethyl acetate-hexane, gave 928 mg of N-[2-chloro-5-(3-dimethylamino-acryloyl)-phenyl]-N-methyl-acetamide as a yellowish-white solid were obtained (yield 88.16%).

¹H NMR (400 MHz, CDCl3): δ 1.79 (3H, s), 2.94 (3H, s), 3.17 (3H, s), 3.19 (3H, s), 5.61 (1H, d, J=12.4 Hz), 7.50 (1H, d, J=8.4 Hz), 7.79-7.85 (3H, m).

MS (ES) m/z=281 (MH+)

HPLC=100%

PREPARATIVE EXAMPLE 4 N-{2-Chloro-5-[3-(thiophene-2-carbonyl)-pyrazolo[1,5-a]pyrimidin-7-yl]-phenyl}-N-methyl-acetamide

A mixture of 0.083 g (0.43 mmol) of (5-amino-1H-pyrazol-4-yl)-thiophene-2-yl-methanone and 0.12 g (0.43 mmol) of N-[2-chloro-5-(3-dimethylamino-acryloyl)-phenyl]-N-methyl-acetamide in 12 ml of glacial acetic acid was refluxed for 1.5 hours and then the solvent was removed by reduced pressure distillation. To the resulting residue were added 15 ml of dichloromethane and 10 ml of saturated sodium bicarbonate solution. The two layers were separated, and the aqueous layer was washed with 10 ml of dichloromethane. The organic layers were washed with 10 ml of water and dried over magnesium sulfate. The dichloromethane layer was evaporated to dryness to yield an oil which, in the presence of ethyl acetate, gave 139 mg of N-{2-chloro-5-[3-(thiophene-2-carbonyl)-pyrazolo[1,5-a]pyrimidin-7-yl]-phenyl}-N-methyl-acetamide as a solid (yield 79%).

¹H NMR (400 MHz, CDCl3): δ 1.92 (3H, s,), 3.27 (3H, s), 7.15 (1H, d, J=4.8 Hz), 7.19-7.21 (1H, m), 7.70-7.71 (1H, m), 7.73 (1H, d, J=8.8 Hz), 8.02 (1H, dd, J=2.4 and 7.6 Hz), 8.06-8.07 (1H, m), 8.12 8(1H, d, J=2 Hz), 8.71 (1H, s), 8.83 (1H, d, J=4 Hz).

MS (ES) m/z=411 (MH+)

HPLC=99.6%

m.p.=191-193° C.

PREPARATIVE EXAMPLE 5 N-[5-(3-Dimethylamino-acryloyl)-2-fluoro-phenyl]-N-methyl-methanesulfonamide

1.66 g (6.77 mmol) of N-(5-acetyl-2-fluoro-phenyl)-N-methyl-methanesulfonamide were dissolved in 3.35 ml (3.0 g) (25.18 mmol) of N,N-dimethylformamide dimethylacetal and the resultant solution was refluxed for 2.5 hours. The mixture was cooled at room temperature. To the solid formed was added 20 ml of n-hexane and filtered to yield a solid which was crystallized from ethyl acetate. 1.37 g of N-[5-(3-dimethylamino-acryloyl)-2-fluoro-phenyl]-N-methyl-methanesulfonamide as a yellowish-white solid were obtained (yield 67.4%).

¹H NMR (400 MHz, CDCl3): δ 2.92 (3H, s), 2.96 (3H, s), 3.15 (3H, s), 3.31 (3H, s), 5.61 (1H, d, J=12.8 Hz), 7.13-7.18 (1H, m), 7.78 (1H, d, J=12.8 Hz), 7.88-7.93 (2H, m).

MS (ES) m/z=301 (MH+)

HPLC=97.99%

PREPARATIVE EXAMPLE 6 N-{2-Fluoro-5-[3-(thiophene-2-carbonyl)-pyrazolo[1,5-a]pyrimidin-7-yl]-phenyl}-N-methyl-methanesulfonamide

A mixture of 0.064 g (0.33 mmol) of (5-amino-1H-pyrazol-4-yl)-thiophene-2-yl-methanone and 0.1 g (0.33 mmol) of N-[5-(3-dimethylamino-acryloyl)-2-fluoro-phenyl]-N-methyl-methanesulfonamide in 10 ml of glacial acetic acid was refluxed for 2.5 hours and then the solvent was removed by reduced pressure distillation. To the resulting residue were added 15 ml of dichloromethane and 10 ml of saturated sodium bicarbonate solution. The two layers were separated, and the aqueous layer was washed with 10 ml of dichloromethane. The organic layers were washed with 10 ml of water and dried over magnesium sulfate. The dichloromethane layer was evaporated to dryness to yield an oil which, in the presence of ethyl acetate, gave 111 mg of N-{2-fluoro-5-[3-(thiophene-2-carbonyl)-pyrazolo[1,5-a]pyrimidin-7-yl]-phenyl}-N-methyl-methanesulfonamide as a solid (yield 77%).

¹H NMR (400 MHz, CDCl3): δ 3.01 (3H, s,), 3.39 (3H, s), 7.13 (1H, d, J=4.4 Hz), 7.18-7.20 (1H, m), 7.36-7.41 (1H, m), 7.70 (1H, dd, J=1.2 and 5.2 Hz), 8.07-8.09 (1H, m), 8.11-8.17 (2H, m), 8.7 (1H, s), 8.80 (1H, d, J=4.8 Hz).

MS (ES) m/z=431 (MH+)

HPLC=98.6%

m.p.=194-196° C.

PREPARATIVE EXAMPLE 7 N-[2-Chloro-5-(3-dimethylamino-acryloyl)-phenyl]-N-methyl-methanesulfonamide

1.0 g (4.04 mmol) of N-(5-acetyl-2-chloro-phenyl)-methanesulfonamide were dissolved in 10 ml of dry N,N-dimethylformamide and 2.69 ml (2.41 g) (20.19 mmol) of N,N-dimethylformamide dimethylacetal. The resultant solution was refluxed for 2 hours. The solvent and the excess of volatile reagent was removed by reduced pressure distillation to yield an oil which, in the presence of ethyl acetate, gave 1.04 of a crude. It was chromatographied (silica gel) using ethyl acetate/2-propanol as eluent. 0.51 g of N-[2-chloro-5-(3-dimethylamino-acryloyl)-phenyl]-N-methyl-methanesulfonamide as a yellowish-white solid were obtained (yield 40%).

¹H NMR (400 MHz, CDCl3): δ 2.9 (3H, s), 3.04 (3H, s), 3.15 (3H, s), 3.3 (3H, s), 5.61 (1H, d, J=12.4 Hz), 7.48 (1H, d, J=8.4 Hz), 7.78 (1H, d, J=12.8 Hz), 7.83 (1H, dd, J=8.8-1.6 Hz), 7.93 (1H, d, J=1.6 Hz).

MS (ES) m/z=317 (MH+)

HPLC=87.58%

PREPARATIVE EXAMPLE 8 N-{2-Chloro-5-[3-(thiophene-2-carbonyl)-pyrazolo[1,5-a]pyrimidin-7-yl]-phenyl}-N-methyl-methanesulfonamide

A mixture of 0.076 g (0.39 mmol) of (5-amino-1H-pyrazol-4-yl)-thiophene-2-yl-methanone and 0.124 g (0.39 mmol) of (N-[2-chloro-5-(3-dimethylamino-acryloyl)-phenyl]-N-methyl-methanesulfonamide in 10 ml of glacial acetic acid was refluxed for 1.5 hours and then the solvent was removed by reduced pressure distillation. To the resulting residue were added 15 ml of dichloromethane and 10 ml of saturated sodium bicarbonate solution. The two layers were separated, and the aqueous layer was washed with 10 ml of dichloromethane. The organic layers were washed with 10 ml of water and dried over magnesium sulfate. The dichloromethane layer was evaporated to dryness to yield an oil which, in the presence of ethyl acetate, gave 128 mg of N-{2-chloro-5-[3-(thiophene-2-carbonyl)-pyrazolo[1,5-a]pyrimidin-7-yl]-phenyl}-N-methyl-methanesulfonamide as a solid (yield 73%).

¹H NMR (400 MHz, CDCl3): δ 3.09 (3H, s,), 3.38 (3H, s), 7.15 (1H, d, J=4.8 Hz), 7.19-7.20 (1H, m), 7.68-7.71 (2H, m), 8.07-8.09 (2H, m), 8.19 (1H, d, J=2 Hz), 8.71 (1H, s), 8.82 (1H, d, J=4.4 Hz).

MS (ES) m/z=447 (MH+)

HPLC=98.1%

m.p.=241-243° C.

PREPARATIVE EXAMPLE 9 N-[5-(3-Dimethylamino-acryloyl)-2-fluoro-phenyl]-N-prop-2-ynyl-methanesulfonamide

1.2 g (4.46 mmol) of N-(5-acetyl-2-fluoro-phenyl)-N-prop-2-ynyl-methanesulfonamide were dissolved in 3 ml (2.7 g) (22.58 mmol) of N,N-dimethylformamide dimethylacetal and the resultant solution was refluxed for 2.5 hours. The mixture was cooled at room temperature and 20 ml of n-hexane were added. The oil obtained was chromatographied (silica gel) using ethyl acetate/2-propanol as eluent. 0.46 g of a yellowish-white solid were obtained. This solid was crystallized in ethyl acetate and 0.213 g of N-[5-(3-dimethylamino-acryloyl)-2-fluoro-phenyl]-N-prop-2-ynyl-methanesulfonamide were obtained (yield 14.7%).

¹H NMR (400 MHz, CDCl3): δ 2.35 (1H, m), 2.92 (3H, s), 3.11 (3H, s), 3.15 (3H, s), 4.43 (2H, m), 5.61 (1H, d, J=12.8 Hz), 7.16-7.21 (1H, m), 7.79 (1H, d, J=12.8 Hz), 7.91-7.94 (1H, m), 8.01-8.04 (1H, m).

MS (ES) m/z=325 (MH+)

HPLC=91.63%

PREPARATIVE EXAMPLE 10 N-{2-Fluoro-5-[3-(thiophene-2-carbonyl)-pyrazolo[1,5-a]pyrimidin-7-yl]-phenyl}-N-prop-2-ynyl-methanesulfonamide

A mixture of 0.108 g (0.56 mmol) of (5-amino-1H-pyrazol-4-yl)-thiophene-2-yl-methanone and 0.198 g (0.61 mmol) of N-[5-(3-dimethylamino-acryloyl)-2-fluoro-phenyl]-N-prop-2-ynyl-methanesulfonamide in 10 ml of glacial acetic acid was refluxed for 2 hours and then the solvent was removed by reduced pressure distillation. To the resulting residue were added 15 ml of dichloromethane and 10 ml of saturated sodium bicarbonate solution. The two layers were separated, and the aqueous layer was washed with 10 ml of dichloromethane. The organic layers were washed with 10 ml of water and dried over magnesium sulfate. The dichloromethane layer was evaporated to dryness to yield an oil which, in the presence of ethyl acetate, gave 156 mg of N-{2-fluoro-5-[3-(thiophene-2-carbonyl)-pyrazolo[1,5-a]pyrimidin-7-yl]-phenyl}-N-prop-2-ynyl-methanesulfonamide as a solid (yield 61%).

¹H NMR (400 MHz, CDCl3): δ 2.39 (1H, s), 3.16 (3H, s,), 4.50 (2H, s), 7.14 (1H, d, J=4.4 Hz), 7.18-7.20 (1H, m), 7.40-7.44 (1H, m), 7.70 (1H, m), 8.07-8.09 (1H, m), 8.18-8.21 (1H, m), 8.24-8.26 (1H, m), 8.7 (1H, s), 8.80 (1H, d, J=4.8 Hz).

MS (ES) m/z=455 (MH+)

HPLC=94.9%

m.p.=149-153° C.

COMPOSITION EXAMPLE 1 5 mg Tablets

Compound of preparative example 2 5.0 mg Colloidal silicon dioxide 0.6 mg Croscarmellose sodium 12.0 mg Talc 4.0 mg Magnesium stearate 1.5 mg Polysorbate 80 1.0 mg Lactose 75.0 mg Hydroxypropyl methylcellulose 3.0 mg Polyethylene glycol 4000 0.5 mg Titanium dioxide E171 1.5 mg Microcrystalline cellulose q.s. to 125.0 mg

COMPOSITION EXAMPLE 2 10 mg Capsules

Compound of preparative example 2 10.0 mg Colloidal silicon dioxide 0.6 mg Crospovidone 12.0 mg Talc 4.0 mg Magnesium stearate 1.5 mg Lauryl sulfate sodium 1.5 mg Lactose 77.0 mg Gelatin 28.5 mg Titanium dioxide E171 1.5 mg Indigotin E132 0.02 mg Microcrystalline cellulose q.s. to 155.0 mg

COMPOSITION EXAMPLE 3 Oral Drops

Compound of preparative example 2 0.5 g Propylene glycol 10.0 g Glycerin 5.0 g Saccharin sodium 0.1 g Polysorbate 80 1.0 g Lemon flavor 0.2 g Ethanol 25.0 ml Purified water q.s. to 100.0 ml

COMPOSITION EXAMPLE 4 2.5 mg Tablets

Compound of preparative example 2 2.5 mg Colloidal silicon dioxide 0.6 mg Croscaramellose sodium 12.0 mg Talc 4.0 mg Magnesium stearate 1.5 mg Polysorbate 80 1.0 mg Lactose 75.0 mg Hydroxypropyl methylcellulose 3.0 mg Polyethylene glycol 4000 0.5 mg Titanium dioxide E171 1.5 mg Microcrystalline cellulose q.s. to 125.0 mg

COMPOSITION EXAMPLE 5 5 mg Capsules

Compound of preparative example 2 5.0 mg Colloidal silicon dioxide 0.6 mg Crospovidone 12.0 mg Talc 4.0 mg Magnesium stearate 1.5 mg Lauryl sulfate sodium 1.5 mg Lactose 77.0 mg Gelatin 28.5 mg Titanium dioxide E171 1.5 mg Indigotin E132 0.02 mg Microcrystalline q.s. to 155.0 mg

COMPOSITION EXAMPLE 6 Oral Drops

Compound of preparative example 2 0.25 g Propylene glycol 10.0 g Glycerin 5.0 g Saccharin sodium 0.1 g Polysorbate 80 1.0 g Lemon flavor 0.2 g Ethanol 25.0 ml Purified q.s. to 100.0 ml 

1. A compound of formula (I):

wherein R represents an alkyl(C₁-C₆); R₁ is selected from the group consisting of alkyl(C₁-C₆) and alkynyl(C₁-C₆); X represents a halogen atom; and Y is selected from the group consisting of —CO— and —SO₂—; and a pharmaceutically acceptable salt thereof.
 2. A compound according to claim 1 wherein R is methyl.
 3. A compound according to claim 1 wherein R₁ is methyl.
 4. A compound according to claim 1 wherein R₁ is prop-2-ynyl.
 5. A compound according to claim 1 wherein X is fluorine.
 6. A compound according to claim 1 wherein X is chlorine.
 7. A compound which is selected from the group consisting of: N-{2-fluoro-5-[3-(thiophene-2-carbonyl)-pyrazolo[1,5-a]pyrimidin-7-yl]-phenyl}-N-methyl-acetamide; N-{2-chloro-5-[3-(thiophene-2-carbonyl)-pyrazolo[1,5-a]pyrimidin-7-yl]-phenyl}-N-methyl-acetamide; N-{2-fluoro-5-[3-(thiophene-2-carbonyl)-pyrazolo[1,5-a]pyrimidin-7-yl]-phenyl}-N-methyl-methanesulfonamide; N-{2-chloro-5-[3-(thiophene-2-carbonyl)-pyrazolo[1,5-a]pyrimidin-7-yl]-phenyl}-N-methyl-methanesulfonamide; and N-{2-fluoro-5-[3-(thiophene-2-carbonyl)-pyrazolo[1,5-a]pyrimidin-7-yl]-phenyl}-N-prop-2-ynyl-methanesulfonamide; and a pharmaceutically acceptable salt thereof.
 8. A process for preparing a compound of formula (I) as defined in claim 1, comprising reacting an intermediate (II):

wherein R, R₁, X and Y are as defined in (I) and Q is an appropriate leaving group selected from the group consisting of N(dialkyl(C₁-C₆)), alkylthio(C₁-C₆) and alkoxy(C₁-C₆), with the intermediate (III):

and alternatively, treatment of the resulting compounds in the form of free base, with an acid to form a salt thereof.
 9. A process according to claim 8, comprising utilizing the intermediate of formula (II) wherein Q is selected from the group consisting of dimethylamino, methylthio and methoxy.
 10. Use of a compound as defined in claim 1, for the preparation of a medicament for treating or preventing anxiety in a mammal.
 11. Use of a compound as defined in claim 1, for the preparation of a medicament for treating or preventing epilepsy in a mammal.
 12. Use of a compound as defined in claim 1, for the preparation of a medicament for treating or preventing sleep disorders in a mammal.
 13. Use of a compound as defined in claim 1, for the preparation of a medicament for treating or preventing insomnia in a mammal.
 14. Use of a compound as defined in claim 1, for the preparation of a medicament for inducing sedation-hypnosis in a mammal.
 15. Use of a compound as defined in claim 1, for the preparation of a medicament for inducing anesthesia in a mammal.
 16. Use of a compound as defined in claim 1, for the preparation of a medicament for modulating the necessary time to induce sleep and its duration in a mammal.
 17. Use of a compound as defined in claim 1, for the preparation of a medicament for inducing muscle relaxation in a mammal.
 18. A pharmaceutical composition comprising a therapeutically effective amount of a compound as defined in claim 1, together with appropriate amounts of pharmaceutically excipients or carriers.
 19. A process for preparing the enaminone intermediate of formula (VI):

wherein R, R₁, X and Y are as described above, by a) reacting the corresponding acetophenone (IV):

wherein R, X and Y are as described above, with N,N-dimethylformamide dimethylacetal or tert-butoxybis(dimethylamino)methane; and b) alkylating the resulting enaminone of formula (V′):

wherein R, X and Y are as described above, via formation of an anion with a hydride compound and subsequent reaction with an alkyl halide of formula ZR₁, wherein Z is a halogen atom and R₁ is as described above.
 20. The process of claim 19 wherein the hydride compound is sodium hydride and Z is iodine.
 21. A process for preparing the enaminone intermediate of formula (VI), according to claim 19, by reacting the corresponding acetophenone (V):

wherein R, R₁, X and Y are as described above, with N,N-dimethylformamide dimethylacetal or tert-butoxybis(dimethylamino)methane.
 22. A process for preparing the enaminone intermediate of formula (VII):

wherein R and X are as defined above, by reacting the acetophenone (IV′):

with N,N-dimethylformamide dimethylacetal.
 23. A process for preparing the enaminone intermediate of formula (X):

wherein R, X and Y are as described above, by: a) reacting the acetophenone (VIII):

wherein X is as defined above, with N,N-dimethylformamide dimethylacetal; and b) alkylating the resulting enaminone of formula (IX):

wherein X is as described above, with the corresponding sulfonic acid or carboxylic acid chloride of formula ClYR, wherein R and Y are as described above.
 24. An intermediate enaminone compound which is selected from the group consisting of: N-[5-(3-dimethylamino-acryloyl)-2-fluoro-phenyl]-N-methyl-acetamide; N-[2-chloro-5-(3-dimethylamino-acryloyl)-phenyl]-N-methyl-acetamide; N-[5-(3-dimethylamino-acryloyl)-2-fluoro-phenyl]-N-methyl-methanesulfonamide; N-[2-chloro-5-(3-dimethylamino-acryloyl)-phenyl]-N-methyl-methanesulfonamide; and N-[5-(3-dimethylamino-acryloyl)-2-fluoro-phenyl]-N-prop-2-ynyl-methanesulfonamide. 